Pursuant to 35 U.S.C. xc2xa7119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application Nos. 55783/1999, filed on Dec. 8, 1999 and 10166/2000, filed on Feb. 29, 2000, the contents of which are hereby incorporated by reference herein in their entirety.
1. Field of the Invention
The present invention relates to a encoder and a decoder considered for the next generation mobile communication system requiring high channel coding performance, in particular to a concatenated convolutional encoder and a decoder of a mobile communication system which is capable of providing a dual mode encoder and a decoder for supporting both a parallel concatenated convolutional code and a serially concatenated convolutional code and improving the performance of the system by using punctured and thrown away sequence in a convolutional encoder.
2. Description of the Prior Art
In a mobile communication system according to the conventional technology, a turbo encoder showing high performance is used for low SNR (Signal to Noise Ratio).
The turbo encoder comprises a parallel concatenated convolutional encoder and a serially concatenated convolutional encoder.
Between them, the serially concatenated convolutional encoder showing continual performance improvement stood in the spotlight because the parallel concatenated convolutional encoder shows a performance saturation phenomenon in high SNR.
The serially concatenated convolutional encoder will now be described with reference to accompanying FIG. 1.
FIG. 1 is a construction profile illustrating the conventional serially concatenated convolutional encoder of the mobile communication system.
As depicted in FIG. 1, the conventional serially 3 of the mobile communication system comprises a first RSC (Recursive Systematic Convolutional) encoder 11 for coding an inputted data sequence DO with xc2xd code rate, a puncturer 12 for puncturing a code outputted from the first RSC encoder 11 with a puncturing pattern 1110 and outputting it, an interleaver 13 for lowering correlation between adjacent data by relocating position of the code outputted from the puncturer 12 after being punctured, and a second RSC encoder 14 for decoding the code relocated by the interleaver 13 with the xc2xd decode rate and outputting the final code CO.
The operation will now be described in detail.
First, when the data sequence DO is inputted to the first RSC encoder 11 the first RSC encoder 11 codes the inputted data sequence DO with xc2xd code rate, generates two new sequences and outputs them. Herein, the two sequences outputted from the first RSC encoder 11 are combined as one sequence by a switch (not shown), and is provided to the puncturer 12.
After that, the puncturer 12 punctures the sequence outputted from the first RSC encoder 11 with the puncturing pattern 1110, and outputs it to the interleaver 13.
Herein, in the puncturing pattern1110, xe2x80x9c1xe2x80x9d means the data outputted from the first RSC encoder 11 is outputted to the interleaver 13 as it is, and xe2x80x9c0xe2x80x9d means the data outputted from the first RSC encoder 11 is punctured, in other words, it is thrown away.
After all, when 4 bits data is outputted from the first RSC encoder 11, the fourth data is thrown away (punctured), and the rest 3 bits are passed.
In addition, the interleaver 13 randomly relocates the data punctured on the multiple proportion bit of 4, reads it to a column direction, and outputs it. Accordingly the interleaver can lower the correlation between the adjacent codes and outputs it to the second RSC encoder 14.
The second RSC encoder 14 codes the code outputted from the interleaver 13 with xc2xd code rate, generates new two sequences, and outputs them. Herein, the outputted two sequences are added by a switch (not shown) as one sequence, and is outputted as a final coded code CO.
Herein, in the conventional serially concatenated convolutional encoder, a encoder of which constraint length is 3 and xc2xd code rate is used, the first RSC encoder 11 and second RSC encoder 14 use the encoder having same construction.
Meanwhile, the conventional parallel concatenated convolutional encoder comprises two RSC encoders and an interleaver. In other words, in the conventional coding technology, after the input sequence of the first convolutional encoder is relocated through the interleaver, the sequence is used as an input sequence of the second convolutional encoder.
Accordingly, because only data part of the output of the first convolutional encoder can be provided to the input of the second convolutional encoder, the system performance lowering problem occurs in the SNR increasing region, accordingly the credibility of the system lowers due to that.
As described above in detail, in the conventional technology, the input sequence of the first convolutional encoder and second convolutional encoder have same weight values, in partucular when the weight value is 2, a code having low weight value about a certain sequence pattern is generated according to the characteristic of the RSC encoder.
In addition, in the conventional technology, because only data part of the output of the first convolutional encoder can be provided to the input of the second convolutional encoder, accordingly the sudden performance lowering problem occurs in the high SNR region.
In addition, in the conventional technology, because the sudden performance lowering problem occurs in the SNR increasing region, accordingly there is a credibility lowering problem due to that.
In addition, in the conventional technology, in the parallel concatenated convolutional encoder, extrinsic information transmitted/received between the each module in iterative decoding only deals with information about the input sequence to the exclusion of information about parity sequence.
In addition, in the conventional technology, the performance of the system lowers due to the sequence punctured by the serially concatenated convolutional encoder.
Accordingly, the object of the present invention is to provide a concatenated convolutional encoder and a decoder of a mobile communication system which is capable of improving performance of the system by using sequence punctured inside of a encoder.
The other object of the present invention is to provide a concatenated convolutional encoder and a decoder of a mobile communication system which is capable of providing a serially convolutional encoder structure having same construction with a parallel concatenated convolutional encoder used in the next generation communication system.
The another object of the present invention is to provide a concatenated convolutional encoder and a decoder of a mobile communication system which is capable of providing single form structure usable as a serially concatenated convolutional encoder and a parallel concatenated convolutional encoder as occasion demands.
The another object of the present invention is to provide a concatenated convolutional encoder and a decoder of a mobile communication system which is capable of multiplexing the output data and parity bit of the first convolutional encoder with an appropriate rate and providing it as an input of the next terminal convolutional encoder.
The another object of the present invention is to provide a concatenated convolutional encoder and a decoder of a mobile communication system which is capable of showing stable performance regardless of SNR fluctuation by setting weight value of the input sequence of the parallel convolutional encoder different from the weight value of the first convolutional encoder in the parallel concatenated convolutional encoder.
In order to achieve the above-mentioned objects, in the concatenated convolutional encoder of the mobile communication system according to the present invention, a serially concatenated convolutional encoder of a mobile communication system for coding an inputted code by puncturing comprises a puncturer for puncturing the inputted code with a certain puncturing pattern, an interleaver for lowering correlation between adjacent bits by relocating position of the code punctured from the puncturer, a first RSC encoder for coding the code outputted from the interleaver with 1/n code rate and outputting it, a delayer for delaying the inputted code punctured and thrown away from the puncturer for a certain time, and a substituent for substituting the punctured code delayed on the delayer for the code on the punctured position when it is inputted among the codes outputted from the first RSC encoder and outputting it.
In order to achieve the above-mentioned objects, a serially concatenated convolutional decoder of a mobile communication system according to the present invention comprises a demux (demultiplexer) and zero inserter for inserting zero on the position of a substituted code bit when the substituted code bit is inputted and outputting it while outputting received code bits, and outputting the substituted code bit to the multiplexer, an inner SISO input unit for generating a decode value by adapting the outputted code bit and a probability value fed-back from an output terminal to a maximum probability decode algorithm, a deinterleaver for deinterleaving the generated decode value, a multiplexer for inserting the substituted code bit into the decode value outputted from the deinterleaver and outputting it, and an outer SISO output unit for generating the final decode value by adapting the decode value having the inserted substituted code bit and probability value of the zero to the maximum probability decode algorithm.
In order to achieve the above-mentioned objects of the present invention, a dual mode concatenated convolutional encoder of a mobile communication system according to the present invention comprises a first RSC encoder for coding inputted data sequence with 1/n code rate, a puncturer for puncturing the code outputted from the first RSC encoder with a certain puncturing pattern, an interleaver for dispersing errors clustered on one code by relocating position of the punctured code, a second RSC encoder for outputting new two code values by coding the error dispersed code with 1/n code rate, a delayer for delaying the code punctured and thrown away from the puncturer for a certain time, a substituent for substituting the punctured code delayed on the delayer for the code on the punctured position when it is inputted among the codes outputted from the second RSC encoder, and outputting it, and a switch for connecting the output of the second RSC encoder and delayer to the substituent in a serial coding mode and connecting directly the output of the second RSC encoder and delayer to an output terminal side in a parallel coding mode.
In order to achieve the above-mentioned objects of the present invention, a decoder of a mobile communication system according to the present invention comprises an encoder for coding input data and outputting it as a code word form, a sequence splitter for outputting a plurality of sequences by splitting the code word, an interleaver for relocating the inputted sequence transmitted as it is among the plurality of the sequences and the rest sequences as a random form, and a certain number of encoder, sequence splitter, interleaver for operating same with the encoder, sequence splitter, interleaver by being dependently connected to an output terminal of the interleaver as many as they are required.